1. Field
The present disclosure relates to a fuel cell.
2. Description of the Related Art
In general, a solid polymer electrolyte fuel cell includes a solid polymer electrolyte membrane, which is a polymer ion-exchange membrane. The fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one surface of the solid polymer electrolyte membrane and a cathode electrode is disposed on the other surface of the solid polymer electrolyte membrane. The anode electrode and the cathode electrode each include a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon).
The membrane electrode assembly and separators (bipolar plates) that sandwich the membrane electrode assembly constitute a power generation cell (unit fuel cell). A predetermined number of power generation cells are stacked and used, for example, as a vehicle fuel cell stack.
In a fuel cell, when forming an anode electrode and a cathode electrode, cracks tend to occur due to, for example, the following factors: the direction in which a catalyst ink is applied; the anisotropy in the length direction (MD) and the width direction (TD) when manufacturing a solid polymer electrolyte membrane and porous carbon; and the sizes, the shapes, and the like of the electrodes.
For example, Japanese Unexamined Patent Application Publication No. 2013-089407 describes a method of manufacturing a membrane electrode assembly, which was devised in order to reduce the occurrence of cracks in a catalyst layer. In this manufacturing method, the concentration of water in a mixed solution used for a catalyst ink is adjusted so that a comparatively small amount of ink is absorbed into an electrolyte membrane. It is described that, by doing so, it is possible to suppress nonuniform expansion and contraction of the electrolyte membrane when the electrolyte membrane absorbs a solvent and to reduce the occurrence of cracks in a catalyst layer formed on the electrolyte membrane.